ENERGY STAR is an international standard for energy efficient consumer products originated in the United States of America. The ENERGY STAR is awarded to lighting products that meet some criteria. The criteria is that illuminating light with eight color temperatures (CT) (2700K, 3000K, 3500K, 4000K, 4500K, 5000K, 5700K, and 6500K) defined by blackbody radiation, and a color rendering index (CRI) of each of the illuminating light is larger than 80. Light colors of traditional light-emitting diode (LED) lighting lamp can be divided into three types: cold white (CT=6500K), warm white (CT=2800K) and white (CT=4000K), and the light colors are generally fixed and unadjustable.
In order to achieve the adjustment of the light colors, the color mixing technology in general is given by mixing light sources of red, green and blue LEDs, and controlling individual luminous intensities of the red, green and blue LEDs to change different colors or color temperatures as desired. However, because each LED has an individual peak wavelength of the color thereof; a spectrum of the light mixed only from the red, green and blue LEDs is not continuous and full spectrum; Accordingly, the color rendering index (CRI) thereof can not be improved.
Thus, there are many techniques that a variety of LEDs are utilized to mix for achieving a high CRI at present. For example, red, amber, blue and green LEDs are used for the color mixing and the light of the LEDs are modulated to the illuminating light with various color temperatures. However, the color rendering indexes of commercial adjustable lighting lamps can not completely meet the criteria of the ENERGY STAR when the lighting lamps are modulated to the above-mentioned color temperatures. That is, the color rendering indexes can reach above 80 only under some color temperatures.
Moreover, in order to reach high color rendering indexes, the lighting lamps that use a plurality of LEDs (more than four LEDs) for the color mixing have been proposed at present, but costs thereof are highly increased. In addition, in the plurality of LEDs, there are some phosphors-doped LEDs, which have a drawback of deterioration easily. Once the phosphors-doped LEDs deteriorate, the whole lighting lamp will generate a serious color shift.
Therefore, the problem that how to create an ENERGY STAR qualified lighting lamp capable of modulating various color temperatures and having a high CRI is actively disclosed in the present invention.